Turbomachines include gas turbine engines, such as auxiliary power units (APU), propulsive gas turbine engines deployed onboard aircraft and other vehicles, turboshaft engines utilized for industrial power generation, and non-gas turbine engine turbomachines, such as turbochargers. Within a turbomachine, various individual components have dedicated functions; examples of the individual components include a fuel pump, hydraulic pump, breather, fuel control unit, combustor housings, oil pump, etc.
During the course of normal operation, some of the turbomachine components may leak or bleed effluent, such as small amounts of fuel, condensation, oil, or the like. A low pressure discharge of air used for controlling seal leakage may also occur. Therefore, normal turbomachine maintenance generally includes inspecting individual components of the turbomachine for leaks and discharge, and assessing, by the presence and quantity of a given leak, whether a problem with the associated component is indicated.
To ease turbomachine maintenance and inspection, drain lines are often attached to relevant components, generally at the gravitationally lowest part of the component. The drain lines may then be routed to a single location, and ganged together on a single drain bracket for convenient access. This drain line grouping is then typically ported out into a dedicated drain cavity called the drain mast. The drain mast allows for passage of drain fluids from an internal aircraft compartment through to the outside of the aircraft skin (fuselage). The aircraft drain mast can be viewed from outside the fuselage to observe telltale signs of effluent, drainage, discharge, or leakage. An external indication of leakage can be followed by an action to access the turbomachine compartment and investigate which APU component may be the source of leakage.
In addition to using drain lines for component leakage, discharge, or effluent, one or more drain lines referred to as an inlet drain lines may respond to negative pressure generated by a turbomachine by drawing air (in-flowing air) into the turbomachine during ground operation of an APU to provide “bleed air” to the environmental control system (ECS) for air conditioning. In these circumstances, the in-flowed air may get mixed with air being fed by the APU plenum that serves as the bleed air source to the ECS for air conditioning.
Even though only small amounts of liquids or fuels are normally released through the effluent drain lines, an undesirable condition occurs when an inlet drain line ingests flammable or odorous fumes from proximate drain lines that have leaked small amounts of fuel, oil, liquids, or particles. This undesirable condition may occur, for example, when the aircraft is not in flight and the APU is running to supply air conditioning, resulting in detectable odors in the cabin of the aircraft. Traditional solutions space the inlet drain lines far from the effluent drains, use multiple seals, or use an additional check valve to isolate an inlet drain line; as such, traditional solutions increase space, weight, and cost, and the associated increase in design complexity impacts the system reliability.
Consequently, a single drain mast seal that provides a fluidly segregated internal chamber for air inlet drain lines is desirable. The desired drain mast seal does not significantly add to the drain mast seal's compressive load and minimizes the drain mast seal's associated three-dimensional space claim, thereby optimizing the APU-to-drain mast interface.